Kevin Flaherty and Tamar Haspel were New Yorkers, Upper West Side; she is a food and women’s health writer for the Washington Post and numerous other publications. He was in the financial industry. Then 2008 happened. They cut their losses and moved to the Cape.

They met Les Hemmila, who owns seven acres of oyster grants in Barnstable, and decided to farm the shellfish themselves.

For three years, Flaherty and Haspel of Barnstable Oyster have produced oysters that they sell to upscale Manhattan restaurants such as Cirque. Haspel says you actually can make a living at it.

We walk down from Mass. Audubon’s Long Pasture Sanctuary’s field overlooking Sandy Neck and Barnstable Harbor to the flats on a program given by the sanctuary early in the evening on July 19. This is one of the many summer classes and events for all ages hosted by Sanctuary Director Ian Ives.

One poetic looking blond in layered frills floats Fellini-like across the mud. She says, “I like the slime. It feels good on my feet.”

We pass a horseshoe crab buried in mud, moonsnail collars, hermit crabs, steamer clam shells, and hordes of mudsnails. A 10-year-old visiting from Connecticut tells his younger brother he has discovered an “exoskeleton” and that it is decidedly of a green crab. There is a pleasant, warm, cocktail hour breeze across the pink sky. The 10-year-old says to the younger sib, “I dare you to eat two oysters. If I eat three, will you eat one?” No response.

Haspel says, “Imagine what it’s like to do this work here in a howling winter wind with a rising tide.” In winter, they stop oystering to take in their equipment. The oysters become dormant at 40 degrees. Seventy thousand young kept in a cooler will be returned to the grant in spring.

Last winter it was so warm they could keep their equipment out on the intertidal flats where 100 acres in back of Sandy Neck are apportioned into two-acre grants. That’s the upside of global warming. (Ives has reminded us that Sandy Neck is 4,000 years old, but that climate may change the harbor, currents and spit alike.)

In front of us are squares of raised wire mesh beds where oysters are growing, about 11 rows of two dozen flats each. Haspel shows us other rows, these of synthetic black mesh bags, some with smaller openings, some larger.

She tells us that oysters release sperm and eggs that fuse, develop a foot which sets them onto a surface; the foot disappears as the oyster couch-potatoes itself permanently to its landing place. Farmed oysters are sterile; the spat look like “quinoa” or “couscous” and are shipped to Haspel and her husband by Fedex, divided out carefully, placed in nylon bags. When they are about a fingernail size (about two months) they are placed in the mesh bags; then at last,when they are large enough to be unlikely prey, they are left to grow on the rectangular rack beds.

Haspel says no matter what different methods of submerging the bivalves are used, the objective is always twofold, to let seawater circulate freely around them so they filter in the nutrients they need, and to protect them from predators such as crabs, conchs, and snails, especially when they are small. (She notes that you seldom see gulls dropping oysters to crack them open. The shells are too hard, unlike clams.)

And filter they do, at between one and two gallons per oyster an hour, filtering up to 50 gallons a day of water (hard to believe!). They have a huge impact on keeping Barnstable Harbor and other water bodies clean.

You don’t need to feed them, but “Oysters like to be touched,” Haspel says, quoting maestro Hemmila. They do need to be moved around in order to grow evenly and in a single layer so they will end up having the aesthetic that chefs like to show on plates.

When they are the legal size of three inches long, they may be harvested. This process usually takes 18 months (Spring to fall of the next year)

Haspel says east coast oysters from the southern U.S. to eastern Canada are all the same species, Crassostrea virginica. The different tastes are due to nutrients, salinity, temperature, even the speed of the tides.

Aphrodisiacs? “Legend.” But Haspel notes they are high in zinc, said to be good for love, and contain certain amino acids shown to raise sex hormone levels in rats. She quips, “Oystering is the world’s second oldest profession,” having been around since at least Roman times.

We come back from the flats to the picnic tables to have a lesson in shucking. Flaherty makes it look easy, pointing the knife (like a painter’s palette blade) in the right direction into the hinge where it stays put, turning just the right way to sever the muscle which opens the shell, and then cutting the other muscle to release the flesh.